Brad DerManouelian <myth at dermanouelian.com> says:
> Yeechang, what kind of drives are in your RAID 5? ATA-133? 7200 RPM? =
> 8MB Cache?
They are Seagate Barracuda.8 400GB PATA drives (I got a fantastic
price on 'em a year ago, the month after their debut). Not far from
the state of the art for drives even today, and needless to say each
with 7200RPM and 8MB cache. I'd be shocked if having gone SATA (and
paying $1000 more for the privilege; like I said, it was a fantastic
price) or another make/model would have made a difference, especiallly
since the 3ware cards virtualize the computer-drive connection into
its own SCSI-like interface regardless of drive. It's not a case of
one drive subtly slowing things down for everything else because a)
iostate measures for all drives are always fairly consistent and the
dd read benchmarks I've done for each drive directly (sd[a-h]) are
consistent. The dd read benchmarks I've done for /dev/md0
interestingly show about twice the performance of
/dev/VolGroup0x/LogVol0x, indicating to me that lvm2 does appear to be
a chokepoint, if not perhaps the only one; rebuilding the array and
doing empirical tests of different RAID/LVM/filesystem configurations
will presumably tell me more.
--
Yeechang Lee <ylee at pobox.com> | +1 650 776 7763 | San Francisco CA US